JSFiddle - React, Tailwind, and code Playground

HTML

<div class="hero"></div>

CSS

body{
    background-color:#eee;
}

.hero {
    position:relative;
    background-color:#659EC7;
    height:100px !important;
    width:100% !important;
}
.hero:after {
    z-index: -1;
    position: absolute;
    top: 100%;
    left: 40%;
    margin-left: -10px;
    content:'';
    width: 0;
    height: 0;
    border-top: solid 10px #659EC7;
    border-left: solid 10px transparent;
    border-right: solid 10px transparent;
}